Method for reactive ion etching and apparatus therefor

ABSTRACT

The invention provides a method for reactive-ion etching a magnetic material with a plasma of a mixed gas of carbon monoxide and a nitrogen-containing compound, the method comprising a step, in which a multilayered film comprising a magnetic material thin film having thereon a resist film formed on a substrate is exposed to an electron beam and then developed, to form a pattern on the resist film, a step, in which a mask material is vacuum deposited, a step, in which the resist is dissolved, to form a mask, and a step, in which a part of the magnetic material thin film that is not covered with the mask is removed by reactive ion etching with a plasma of a mixed gas of carbon monoxide and a nitrogen-containing compound, to form a pattern on the magnetic material thin film, and thus obtaining the magnetic material thin film finely worked.

FIELD OF THE INVENTION

[0001] The present invention relates to a mask for reactive ion etchingand an apparatus used therefor. More specifically, the invention relatesto a novel mask for reactive ion etching and an apparatus used therefor,which is characterized by a dry etching apparatus for a magneticmaterial, which is useful for production of a magnetic head forread-write of a magnetic disk, a microtrans former or a microinductorinstalled in a magnetic integrated circuit, a magnetic sensor, variousquantum magnetic devices, such as a spin scattering magnetoresistanceeffect device, a spin valve device, a ferromagnetic tunneling device, aspin diode and a spin transistor, and a constitutional part of amicromachine, such as a thin film magnet and a magnetostrictiveactuator.

BACKGROUND OF THE INVENTION

[0002] A microsemiconductor device such as a VLSI and a micromagneticdevice are generally produced by a combination of two processes, i.e., alithography technique and an etching technique.

[0003] The lithograph technique is a technique of producing finepatterns on a photosensitive film such as a resist film coated on asurface of a material to be processed, such as a thin film of asemiconductor and a thin film of a magnetic material, which includes aphotolithography technique where exposure is conducted with anultraviolet ray, an electron beam lithography technique where exposureis conducted with an electron beam, and an ion beam lithographytechnique where exposure is conducted with an ion beam.

[0004] The etching technique is a technique of producing a device bytransferring the resist pattern produced by the lithography to thematerial to be processed, such as a thin film of a semiconductor and athin film of a magnetic material.

[0005] The etching technique includes a wet etching method, an argon ionmilling method and a reactive ion etching method. Among these etchingmethods, the reactive ion etching method is the most excellent methodbecause the pattern produced by the lithography can be transferred inthe most precise manner, it is most suitable for fine working, and theetching rate is the largest. LSIs of semiconductors and semiconductormemory devices are actually produced by this method.

[0006] In the reactive ion etching method, a material to be processed isplaced in a plasma of a reactive gas with applying an electric field,and atoms on the surface of the material to be processed is chemicallyand physically removed by an ion beam incident normally onto the surfaceof the material to be processed, by which an anisotropic working ispossible, where a part not covered with the mask is vertically cut alongthe edge of the mask. Accordingly, a fine and sharp feature can betransferred by the reactive ion etching method. In the reactive ionetching method, chemical active species such as an ion and a radical ofthe reactive gas generated in the plasma are adsorbed on the surface ofthe material to be processed, to chemically react with the material tobe processed, and a surface reactive layer having a lower bond energy.The surface of the material to be processed is exposed to the impact ofcations accelerated by the electric field in the plasma, and thus thesurface reactive layer having a lower bond energy is removed by thesputtering effect by ions or the evaporation effect of itself. That is,the reactive ion etching method is a process, which proceeds with achemical action and a physical action simultaneously. As a result, theselectivity of etching only a specific material, and the anisotropy ofvertically etching the surface of the material to be processed can berealized.

[0007] However, an effective reactive ion etching method has not beendeveloped for a magnetic material for a long time. The wet etchingmethod or the argon ion milling is actually used for a magneticmaterial, to produce a thin film magnetic head, a magnetic sensor and amicrotrans former.

[0008] Under the circumstances with respect to a magnetic material, thetendencies of the miniaturization and the high density integration of amagnetic material is considerably delayed, which becomes a difficulty ofdevelopment of these devices.

[0009] The reason why the reactive ion etching of a magnetic material isdifficult is as follows. While the magnetic material mainly composed ofa transition metal element can react with most of etching gases havingbeen developed for etching semiconductor materials (e.g., CF₄, CCl₄,CCl₂F₂, CClF₃, CBrF₃, Cl₂, C₂F₆, C₃F₈, C₄F₁₀, CHF₃, C₂H₂, SF₆, SiF₄,BCl₃, PCl₃, SiCl₄, HCl and CHClF₂), only a reaction product having a farlarger bond energy than the reaction product of the semiconductormaterial is produced. Therefore, it cannot be removed by the sputteringor the evaporation, and etching cannot proceed.

[0010] Under the circumstances, an investigation of a novel reactive ionetching process has been investigated that is not analogical inferenceof the existing technique for semiconductors, and recently a methodusing a plasma of a mixed gas of carbon monoxide (CO) and ammonia gas(NH₃) has been developed by the inventor of the invention. The principalof this method is that a carbonyl compound of a transition metal (e.g.,Fe(CO)₅, Ni(CO)₄, Co₂(CO)₈, Mn₂(CO)₁₀, Cr(CO)₆, V(CO)₆, Mo(CO)₆ andW(CO)₆) is formed on the surface of the magnetic material mainlycomposed of a transition metal element as a material to be processed byan active radial of CO, which is then removed by the evaporation or thesputtering of an ion in vacuum, to proceed etching. The carbonylcompound of a transition metal is the compound having the smallest bondenergy among the transition metal compounds. However, since CO isdecomposed to CO₂ and C through a disproportionation reaction, anintroduced CO gas does not contribute to the reaction, and the free Catom reacts with the transition metal element to form a stabletransition metal carbide, and therefore an etching reaction does notproceed in general. The NH₃ gas plays a role of delaying thedisproportionation reaction in the presence of the transition metalelement, and the objective reactive ion etching can proceed in theplasma of a gas obtained by mixing the substantially same amounts of COgas and NH₃ gas.

[0011] By a method according to this principal, it has been confirmedthat magnetic materials, such as a permalloy (Fe—Ni alloy), a Co—Cralloy and Fe, can be subjected to the reactive ion etching. As a resultof the development of such an excellent reactive ion etching method fora magnetic material, further technical development of the method hasbeen expected. However, this method involves a problem in that theetching rate is not so large, for example, 34 nm/min, although workingof fine patterns and anisotropic shapes can be realized.

[0012] Furthermore, in the conventional etching method using the CO—NH₃mixed gas plasma, an SiO₂ film produced by a sputtering method has beenused as a mask material that is difficult to suffer the etchingreaction, and there is a problem in that the working precision andproductivity of the SiO₂ film are limited.

[0013]FIG. 2 shows a schematic flow diagram of the conventional process.

[0014] In step (a) of FIG. 2, on a substrate material such as Corning7059 glass substrate 1, a ferromagnetic thin film to be processed suchas a permalloy (Fe—Ni alloy) 2 is formed by a sputtering method, aquartz (SiO₂) thin film 3 as a mask material and a conductive materialsuch as an amorphous carbon film 4 are formed in this order by asputtering method, and a resist 5 as an electron beam-sensitive film iscoated, for example, by a spin coating method. The amorphous carbon film4 is a conductive layer necessary for not charging the material to beprocessed on electron beam exposure, which becomes necessary since thequartz (SiO₂) film 3 is an insulating material. In step (b) of FIG. 2, adesired pattern is formed on the resist by electron beam writing anddevelopment. The amorphous carbon layer is etched by oxygen-ion etchingwith using the resist pattern as a mask, to expose the SiO₂ film alongwith the pattern (step (c) in FIG. 2). The SiO₂ film is then etched withcarbon tetrafluoride (CF₄), for example, to transfer the pattern ontothe SiO₂ film. The ion etching with CF₄ is effective only to the SiO₂film, and the permalloy as the objective material to be processed is notchanged (step (d) of FIG. 2).

[0015] The pattern transferred to the SiO₂ film is then transferred ontothe permalloy with using the patterned SiO₂ as a mask by the reactiveion etching method using the CO—NH₃ mixed gas plasma described above.The resist film and the amorphous carbon film are also removed throughthe reactive-ion etching, and the SiO₂ remains on the patternedpermalloy, to complete the transfer of the pattern (step (e) of FIG. 2).The fine working with reactive-ion etching of a magnetic material, suchas a permalloy (Fe—Ni alloy), a Co—Cr alloy and Fe, has been conductedaccording to this conventional process.

[0016] However, the conventional process involves a problem in that notonly the process is complicated with deteriorated productivity, but alsosince the transfer is twice performed, high precision of a transferredpattern cannot be obtained. In the conventional process, a patterncorresponding to the part that is has not been exposed to an electronbeam finally remains, and as a result, the inverted pattern of thepattern exposed to an electron beam, i.e., a negative pattern, isprovided. However, in the course of the production of a complicated andfine structure of a magnetic material, it is also necessary to provide apattern corresponding to the part that has been exposed to an electronbeam, i.e., a positive pattern.

SUMMARY OF THE INVENTION

[0017] An object of the invention is to solve the problems associatedwith the conventional techniques, and to provide a novel mask material,a process technique using the same, and an apparatus therefor thatrealize effective reactive ion etching of a magnetic material with alarge etching rate, etching with ease and a high resolution andprecision, and provision of a positive pattern.

[0018] The invention relates to a method for reactive ion etching amagnetic material with a plasma of a mixed gas of carbon monoxide and anitrogen-containing compound,

[0019] the method comprising

[0020] a step, in which a multilayered film comprising amagneticmaterial thin film having thereon a resist film formed on a substrate isexposed to an electron beam and then developed, to form a pattern on theresist film,

[0021] a step, in which a mask material is vacuum deposited,

[0022] a step, in which the resist is dissolved, to form a mask, and

[0023] a step, in which a part of the magnetic material thin film thatis not covered with the mask is removed by reactive-ion etching with aplasma of a mixed gas of carbon monoxide and a nitrogen-containingcompound, to form a pattern on the magnetic material thin film, and thusobtaining the magnetic material thin film finely worked.

[0024] In the method for reactive-ion etching of the invention describedabove, the mask used in the reactive ion etching may comprise at leastone member selected from the group consisting of titanium, magnesium,aluminum, germanium, platinum, palladium, an alloy comprising at leastone of them as a main component, and a compound thereof.

[0025] In the method for reactive-ion etching of the invention, the maskused in the reactive-ion etching may comprise silicon or an alloycomprising silicon as a main component.

[0026] In the method for reactive-ion etching of the invention, the maskused in the reactive-ion etching may comprise a compound of silicon, andmay be disposed on the pattern formed on the resist film and formed intothe mask by a lift-off method.

[0027] The invention also relates to an apparatus for reactive ionetching comprising a reaction chamber and metallic parts contained inthe reaction chamber, the whole or a part of which comprises at leastone metallic material selected from the group consisting of titanium,aluminum, and an alloy comprising at least one of them as a maincomponent.

[0028] In the apparatus for reactive ion etching of the inventiondescribed above, a surface layer of the whole or a part of the reactionchamber and metallic parts contained in the reaction chamber comprisesthe at least one metallic material.

[0029] In the apparatus for reactive-ion etching of the invention, asusceptor for supporting a material to be etched comprises at least onemetallic material described above. In the apparatus for reactive ionetching of the invention, at least one of a high frequency electrode, ahigh frequency antenna, an ground electrode, a zero potential shield anda protective plate comprises the at least one metallic materialdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a schematic flow diagram of a fine working of a magneticmaterial according to one embodiment of the invention.

[0031]FIG. 2 is a schematic flow diagram of a fine working of a magneticmaterial according to the conventional process.

[0032]FIG. 3 is a schematic cross sectional view of an apparatus forreactive-ion etching of a parallel flat plates type according to oneembodiment of the invention.

[0033]FIG. 4 is a schematic cross sectional view of an apparatus forreactive ion etching of an inductive coupling type according to oneembodiment of the invention.

[0034]FIG. 5 is a schematic cross sectional view of an apparatus forreactive ion etching of an electron cyclotron resonance type accordingto one embodiment of the invention.

[0035]FIGS. 6A, 6B and 6C are electron micrographs showing etch featuresof magnetic materials.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The invention relates to a mask for reactive-ion etching used onetching a magnetic material by a reactive-ion etching method using aplasma of a mixed gas of carbon monoxide and a nitrogen-containingcompound, and an apparatus for reactive-ion etching.

[0037] The invention is described in detail below.

[0038] (a) Mask for Reactive Ion-Etching

[0039] A mask substance having been generally used in the semiconductortechnique is a resist itself, which is a polymer material. However, thevarious polymer resists cannot be used as a mask in a CO—NH₃ gas plasmadue to its large loss. Metallic elements, such as Cr, W, Mo, Mn, Nb, Ta,Fe, Ru, Os, Co, Rh, Ir, Ni, Cu, Ag, Au, Ga, In and Sn, and an alloy orcompound comprising them as a main component are not suitable as themask material because they react with the CO—NH₃ gas plasma andthemselves are etched by the sputtering action to be worn out. Metallicelements, such as Zn, Cd and Pb, and an alloy or compound comprisingthem as a main component are also not suitable because they are poor inresistance in vacuo. On the other hand, it has been found fromexperimental results that Ti, Mg, Al, Si, Ge, Pt, Pd, an alloycomprising at least one of them as a main component, and a compoundthereof are suitable as the mask material because they are difficult toreact with the CO—NH₃ gas plasma. Among these, the most preferred are Tiand an alloy or a compound comprising Ti as a main component in view ofthe requirements of chemical stability, dense packing of crystallinegrains, and difficulty of generation of pinholes.

[0040] In the invention, the mask may comprise at least one memberselected from the group consisting of Ti, Mg, Al, Ge, Pt, Pd, an alloycomprising at least one of them as a main component, and a compoundthereof. For example, the mask comprises at least one of a single metalof Ti, Mg, Al, Ge, Pt or Pd, a Ti alloy, a Mg alloy, an Al alloy, a Gealloy, a Pt alloy, a Pd alloy, a Ti—Mg alloy, a Ti—Al alloy, a Ti—Gealloy, a Ti—Pt alloy, a Ti—Pd alloy, a Mg—Al alloy, a Mg—Ge alloy, aMg—Pt alloy, a Mg—Pd alloy, an Al—Ge alloy, an Al—Pt alloy, an Al—Pdalloy, a Ge—Pt alloy, a Ge—Pd alloy, a Ti—Mg—Al alloy, a Ti—Al—Ge alloy,a Ti—Mg—Ge alloy, a Ti—Mg—Pt alloy, a Ti—Al—Pd alloy, a Mg—Al—Ge alloy,TiO₂, Mgo, MgF₂, Al₂O₃, TiN, AlN, MgN, GeO₂ and PdO. The term “at leastone” used herein means that the whole mask may comprise only one memberof them, and the mask may comprise plural kinds of them, which mayconstitute part by part of the mask, may constitute a laminatedstructure, or may constitute the exposed surface layer of the mask.

[0041] In the invention, the mask may also comprise silicon or an alloycomprising silicon as a main component, as well as a compound ofsilicon, such as SiO₂ and Si₃N₄. Preferred example of the alloy ofsilicon include those comprises silicon and the above-described metallicelements, e.g., Ti, Mg, Al and Ge, such as a Ti—Si alloy, a Si—Al alloy,a Si—Ge alloy, a Si—Pt alloy, a Si—Pd alloy, a Ti—Si—Al alloy, aTi—Mg—Si alloy and an Al—Mg—Si alloy.

[0042] While SiO₂ has been considered as a material for a mask, it hasbeen used in the method in which the pattern is twice transferred. Inthe invention, on the other hand, it is used as a novel mask by usingthe lift-off method.

[0043] The mask can be formed by various methods, such as vacuumdeposition, sputtering, ion plating or ion-beam deposition.

[0044]FIG. 1 shows one embodiment of a schematic flow diagram of thefine working with respect to the mask of the invention.

[0045] In step (a) of FIG. 1, a magnetic material thin film 2 as amaterial to be subjected to the fine working is formed on a substratematerial 1 such as Corning 7059 glass, and a resist film 5 is coatedthereon, for example, by a spin coating method. The resulting multilayeris exposed to an electron beam, and then developed, to form a desirepattern 6 on the resist film 5 (step (b) of FIG. 1). A mask material 7such as Ti is vapor deposited (step (c) of FIG. 1), and a Ti mask 8 isformed by a lift-off method, i.e. dissolution of the polymer resist(step (d) of FIG. 1). A part of the magnetic material thin film that isnot covered with the Ti mask is removed by reactive-ion etching with aCO—NH₃ mixed gas plasma, to form a pattern on the magnetic material thinfilm, and thus obtaining the magnetic material thin film 9 finely worked(step (e) of FIG. 1). The Ti mask remains as not removed in this stage.The remaining Ti mask is removed, if necessary, for example, by aconventional reactive etching method using a CCl₄ gas plasma (step (f)of FIG. 1).

[0046] In any embodiment of the invention, no redeposition layers or acontamination on the surface of the etched feature are observed, andetching with a sharp and a precise shape can be realized. Representativeexample of the material to be etched in the invention is a magneticmaterial including a magnetic material comprising a transition metal asa main component, such as permalloy, Fe, Ni, Co, a Co—Cr alloy, asendust alloy, Mo, a rare earth element, an alloy or a compound of theseelements.

[0047] As the resist film used for forming the mask pattern, variousorganic polymer films utilizing the conventional exposure-developmentsystem may be used. It may be formed by direct formation of the maskpattern. As the plasma gas for etching, a mixed gas of CO and anitrogen-containing compound, such as NH₃ or an amine, is preferablyused for etching a magnetic material.

[0048] (b) Apparatus for Reactive Ion Etching

[0049] An apparatus for reactive ion etching used in the fine workingprocess of the invention at the step (e) of FIG. 1, i.e. the reactiveion etching using the CO—NH₃ mixed gas plasma, is described.

[0050] In the conventional apparatus for reactive ion etching, thereaction chamber and constitutional parts contained in the reactionchamber are composed of stainless steel. Stainless steel is an alloycomprising iron, nickel and chromium, which are transition metals, andthus has a composition similar to a magnetic material. Therefore, if thereactive ion etching to a magnetic alloy mainly composed of a transitionmetal with the mixed gas plasma of CO and NH₃ is conducted by using theconventional apparatus for reactive-ion etching, not only the materialto be etched but also the reaction chamber, an electrode, a susceptorsupporting the material to be etched, and other peripheral parts exposedto the plasma are subjected to the action of the ion etching.Accordingly, a problem arises in that the interior of the reactionvessel is corroded, and at the same time, the whole of the reactive gasplasma cannot be effectively used for etching of the material to beetched. This also becomes a factor of contamination of the material tobe etched and brings about various unfavorable results such as reductionin etching rate.

[0051] In the invention, to solve the problems described above, titanium(Ti), a Ti alloy, aluminum (Al), an aluminum alloy or a Ti—Al alloy isused for at least a part of the reaction chamber and constitutionalparts contained in the reaction chamber instead of stainless steel usedin the conventional apparatus.

[0052] The term “a part” used herein means, in view of the object of theinvention, a portion or a part that is liable to receive the etchingaction of a plasma of a mixed gas of CO and NH₃ or a mixed gas of CO anda nitrogen-containing compound, such as an amine, and adversely affectson the reactive ion etching. Therefore, it can be understood in thepractical constitution of the apparatus that the whole or a part of themain body of the reaction chamber, its inner surface, an inlet systemand an exhaust system of the gas, and various parts disposed in thechamber are made of the above-described metals, with taking the systemof generation and introduction of the plasma and the species and thesize of the material to be etched into consideration.

[0053] For example, FIGS. 3, 4 and 5 show embodiments of the apparatusof the invention, which are a parallel flat plates type plasmaapparatus, an inductive coupling type plasma apparatus, and an electroncyclotron resonance type plasma apparatus, respectively. In theseapparatuses, the portions and the parts described below are composed ofTi, Al, a Ti alloy, an Al alloy or an Ti—Al alloy, except for anon-metallic part such as glass or cooling water.

[0054] In FIGS. 3, 4 and 5, numeral 10 denotes a reaction chamber, 11denotes a protective plate, 12 denotes a ground electrode, 13 denotes asupporting plate, 14 denotes a high frequency electrode, 15 denotes azero potential shield, 16 denotes a conductance adjusting valve, 17denotes a window flange or a feed-through flange, 18 denotes an inlet ofa reaction gas, 19 denotes a view port, 20 denotes a high frequencypower source, 21 denotes cooling water, 22 denotes a coil antenna, 23denotes a quartz window, 24 denotes a solenoid coil, and 25 denotes amicrowave waveguide.

[0055] As a result of actual experiments with respect to Ti, Al, Cu andthe conventional stainless steel, in the case where all the metallicparts contained in the reaction chamber, e.g. a susceptor supporting thematerial to be etched, a high frequency electrode, a zero potentialshield, and a ground electrode, as well as struts, shutters, bolts andnuts, were composed of Ti, the most excellent function of the inventionwas obtained. That is, in the process of reactive ion etching, the ratioof the loss of these parts made of Ti due to corrosion was as small asit cannot be observed in comparison to stainless steel, and the etchingrates of a permalloy (80% Ni—Fe alloy) and a 10% Cr—Co alloy as amaterial to be etched were 120 nm/min and 140 nm/min, respectively,which were 4 times larger than that of the conventional apparatus usingstainless steel. Furthermore, no redeposition layers on the surface ofthe etched feature observed, and etching with a sharp and preciseprofile could be realized. The parts that exhibit the most considerableinfluence on the function of the invention are a susceptor supportingthe material to be etched, and a ground electrode. In order toconstitute these parts, Ti is preferred from the standpoint of itsexcellent resistance in vacuum, mechanical strength, weldability andworkability of bending and cutting. In addition to pure Ti, various Tialloys that satisfy the conditions above can be used in the invention.Preferred examples of the Ti alloy include a Ti—Pd alloy, a Ti—Ta alloy,a Ti—Al—Sn alloy, a Ti—Al—V—Mo alloy, a Ti—Al—Sn—Zr—Mo—Si alloy, aTi—Al—Zr—Mo—Sn alloy, a Ti—Al—V alloy, a Ti—Al—Sn—Zr—Mo alloy, aTi—Al—V—Sn alloy and a Ti—V—Cr—Al alloy.

[0056] While pure Al also exhibit the similar function, it should becarefully handled with respect to the weldability and the strength incomparison to Ti. In addition to pure Al, the same function can beobtained by using alloys, such as an Al—Cu—X₁ alloy (where X₁ is anadditive element, e.g. Si, Mn and Mg), an Al—Mn—X₂ alloy (where X₂ is anadditive element, e.g. Mg and Si), an Al—Mg—X₃ alloy (where X₃ is Zn,Si, Cr, Mn or Mg), and an Al—Si—X₄ alloy (where X₄ is an additiveelement, e.g. Mg, Cu and Cr).

[0057] Pure Cu and alloys composed of Cu as a main component do notexhibit any notable function in comparison to stainless steel.

[0058] In the invention, according to the constitution described in theforegoing, a novel mask material, a process technique using the maskmaterial, and an apparatus therefor are provided, that realize effectivereactive-ion etching of a magnetic material with a large etching rate,etching with ease and high resolution and precision, and provision of anpositive pattern. The constitution and function of the invention isdescribed in more detail referring to the following examples, but theinvention is not construed as being limited thereto.

EXAMPLE 1 Fine Working of Fe Thin Film Using Ti Mask

[0059] Reactive ion etching was conducted according to the process shownin FIG. 1 using the apparatus for reactive ion etching of the invention.In the apparatus, the reaction chamber and all the parts containedtherein are made of pure Ti.

[0060] An Fe thin film having a thickness of 450 nm was formed as aferromagnetic material thin film 2 on Corning 7059 glass substrate 1 bya sputtering method. After forming a resist film 5, a pattern 6 of theresist film was formed by electron beam lithography. By using Ti as amask material 7 formed on the pattern 6, a mask 8 composed of a numberof small Ti pads was formed by a lift off method. The resulting samplewas placed on a lower electrode cooled by water, powered by a highfrequency of 13.56 MHz. The distance between the high frequencyelectrode and a ground electrode was set to 35 mm. With supplying a COgas and an NH₃ gas into the reaction chamber at flow rates of 6.3 cc/minand 6.8 cc/min, respectively, the pressure of the reaction gas in thechamber was maintained at a pressure of 5.7×10^(0.3) Torr by evacuatingwith a turbo-molecular pump. A high frequency of 3.7 W/cm² was appliedto the lower electrode supporting the sample, to generate aglow-discharge plasma of the CO—NH₃ mixed gas, and thus reactive-ionetching was conducted. The time of etching process was 4.0 minutes.

[0061] After the etching was conducted according to the above-describedprocess, step heights between the part covered with the Ti pad used asthe mask 8 and the part not covered with it were measured by amultiple-beam reflection interferometer, to obtain an etching rate. Thefeatures formed by etching were observed with an electron-beammicroscope, to evaluate the etching for flatness and sharpness of thesteps, and a contamination or a redeposition layer. As a result ofetching, a patterned Fe thin film was obtained as a finely workedmagnetic material 9. The etching rate for the Fe thin film was 90nm/min. The etching feature having a sharpness with a radius ofcurvature of about 0.1 μm and a depth of 400 nm was obtained.

[0062]FIGS. 6A, 6B and 6 c are electron-beam micrographs showing theresults of etching of the following thin films with using the Ti mask.

[0063]FIG. 6A: Fe thin film;

[0064]FIG. 6B: Co-9.8% Cr thin film;

[0065]FIG. 6C: Ni-20% Fe thin film.

[0066] It can be understood from the micrographs that excellent workingprecision can be obtained.

COMPARATIVE EXAMPLE 1 Fine Working of Permalloy (Ni-20% Fe alloy) ThinFilm Using Ti Mask

[0067] The reactive ion etching of an Ni-20% Fe alloy was possible underthe same conditions as in Example 1. The etching rate was 120 nm/min andthe shape obtained by etching was excellent.

COMPARATIVE EXAMPLE 2 Fine Working of Co-9.8% Cr alloy Thin Film UsingTi Mask

[0068] The reactive ion etching of a Co-9.8% Cr alloy was possible underthe same conditions as in Example 1. The etching rate was 140 nm/min andthe shape obtained by etching was excellent.

EXAMPLE 2 Fine Working of Ni-20% Fe alloy Thin Film Using Al Mask

[0069] Aluminum was vacuum deposited and an Al mask was formed by a liftoff method under the same conditions as in Example 1. The reactive ionetching of a Ni-20% Fe alloy was possible under the same conditions asin Example 1. The etching rate was 120 nm/min and the shape obtained byetching was excellent.

EXAMPLE 3 Fine Working of Co-9.8% Cr alloy Thin Film Using Si Mask

[0070] Silicon was vacuum deposited and an Si mask was formed by a liftoff method under the same conditions as in Example 1. The reactive ionetching of a Co-9.8% Cr alloy was possible under the same conditions asin Example 1. The etching rate was 140 nm/min and the shape obtained byetching was excellent.

EXAMPLE 4 Fine Working of Co-9.8% Cr alloy Thin Film Using Ge Mask

[0071] Germanium was vacuum deposited and a Ge mask was formed by alift-off method under the same conditions as in Example 1. Thereactive-ion etching of a Co-9.8% Cr alloy was possible under the sameconditions as in Example 1. The etching rate was 140 nm/min and theshape obtained by etching was excellent.

[0072] As described in detail in the foregoing, the reactive ion etchingof a magnetic material using a CO—NH₃ mixed gas plasma and the like canbe more effectively conducted by using the apparatus for reactive-ionetching according to the invention, in comparison to the case using theconventional reactive ion etching apparatus. That is, the etching ratecan be increased by about 4 times under the same conditions, tocontribute to the working efficiency. Furthermore, the material to beetched is not contaminated during the etching process, and theredeposition layer removed by the etching can be reduced to the levelthat does not bring about a problem.

[0073] According to the function described in the foregoing, theproduction of a micro magnetic head, a microtrans former, a micromagnetic device, a magnetic sensor, a magnetoresistance device, a spindiode, a spin transistor, a spin valve device, a spin valve magneticmemory and a magnetoresistance tunneling effect device can be possible.The production of a patterned magnetic recording medium of a highdensity magnetic recording medium that is being developed can also bepossible.

What is claimed is:
 1. A method for reactive ion etching a magneticmaterial with a plasma of a mixed gas of carbon monoxide and anitrogen-containing compound, said method comprising a step, in which amultilayered film comprising a magnetic material thin film havingthereon a resist film formed on a substrate is exposed to an electronbeam and then developed, to form a pattern on said resist film, a step,in which a mask material is vacuum deposited, a step, in which saidresist is dissolved, to form a mask, and a step, in which a part of saidmagnetic material thin film that is not covered with said mask isremoved by reactive ion etching with a plasma of a mixed gas of carbonmonoxide and a nitrogen-containing compound, to form a pattern on saidmagnetic material thin film, and thus obtaining said magnetic materialthin film finely worked.
 2. A method for reactive ion etching as claimedin claim 1, wherein said mask used in said reactive ion etchingcomprises at least one member selected from the group consisting oftitanium, magnesium, aluminum, germanium, platinum, palladium, an alloycomprising at least one of them as a main component, and a compoundthereof.
 3. A method for reactive-ion etching as claimed in claim 1,wherein said mask used in said reactive-ion etching comprises silicon oran alloy comprising silicon as a main component.
 4. A method forreactive-ion etching as claimed in claim 1, wherein said mask used insaid reactive ion etching comprises a compound of silicon, and isdisposed on said pattern formed on said resist film and formed into saidmask by a lift off method.
 5. An apparatus for reactive-ion etchingcomprising a reaction vessel and metallic parts contained in saidreaction vessel, the whole or a part of which comprises at least onemetallic material selected from the group consisting of titanium,aluminum, and an alloy comprising at least one of them as a maincomponent.
 6. An apparatus for reactive-ion etching as claimed in claim5, wherein a surface layer of said whole or a part of said reactionvessel and said metallic parts contained in said reaction vesselcomprises said at least one metallic material.
 7. An apparatus forreactive-ion etching as claimed in claim 5 or 6, wherein a susceptor forsupporting a material to be etched comprises said at least one metallicmaterial.
 8. An apparatus for reactive-ion etching as claimed in claim 5or 6, wherein at least one of a high frequency electrode, a highfrequency antenna, an ground electrode, a zero potential shield and aprotective plate comprises said at least one metallic material.